Heretofore, polyvinyl chloride (PVC) has typical)y been produced in large reaction vessels. A problem often encountered is a formation of gel during the polymerization of the resin. Gel can be reduced by thoroughly cleaning the reaction vessel periodically or after every production run. However, cleaning of the reaction vessels requires extensive down time and severely hinders the production rate of the resin.
It is known that the use of secondary dispersants enhance build-up on reactor walls which result in fisheyes in subsequent charges. Accordingly, the reactor must be periodically opened and cleaned.
U.S. Pat. No. 4,824,878 to Biaggi relates to a process for producing vinyl chloride polymer by polymerizing the monomer in an aqueous suspension in the presence of a free radical catalyst, a primary suspending agent to control the granulometric distribution of the particles of polyvinyl chloride obtained, as well as a secondary suspending agent consisting of partially hydrolyzed polyvinyl acetate having a saponification number between 520 and 600.
U.S. Pat. No. 4,345,056 to Thyret relates to a process for suspension polymerization of vinyl chloride employing mixed protective colloids such as polyvinyl acetate having a hydrolysis degree of 40 to 55 mole percent. With the remainder of the protective colloid mixture being a water soluble polyvinyl alcohol, an aminoethyl-hydroxypropyl cellulose and a vinyl acetate/vinyl pyrrolidone copolymer. The polyvinyl chloride produced allegedly has a low number of specks.